This invention relates to an industrial burner of the type in which a mixture of gaseous fuel and combustion air is ignited at the face of a nozzle to produce a flame for heating air, for drying material or for various other industrial purposes. Such a burner may be of a nozzle mix design or a premix design. In a nozzle mix design, fuel and combustion air are first mixed at the face of the nozzle and then are ignited to produce a stable flame. In a premix design, the fuel and combustion air are well mixed before being discharged through the nozzle for ignition at the face thereof.
Environmental requirements dictate that such burners operate with significantly reduced emissions of carbon monoxide (CO) and nitrogen oxides (NO.sub.x). Due to variations in the combustion process and flame geometry, the formation of CO and NO.sub.x changes as a function of fuel input to the burner. When a burner is fired at a low level, formation of NO.sub.x is comparatively insignificant while the formation of CO is relatively high as a result of the quenching effect of the incoming combustion air. At higher firing levels, CO emissions are reduced but NO.sub.x emissions increase.